Low profile tri-axis actuator for folded lens camera

ABSTRACT

Folded camera modules in which the camera module height is determined by a folded lens module diameter and by the lens module movement in a direction perpendicular to the lens optical axis, and dual-aperture cameras including such folded camera modules. A folded camera module includes OIS and AF actuators having dimensions smaller than the camera module height and therefore not adding to the camera module height.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/310,902filed Nov. 14, 2016 (now allowed), which was a 371 application frominternational patent application PCT/IB2016/053335, and is related toand claims priority from U.S. Provisional Patent Application No.62/183,974 filed on Jun. 24, 2015, which is expressly incorporatedherein by reference in its entirety.

FIELD

Exemplary embodiments disclosed herein relate in general to digitalcameras and in particular to optical image stabilization (OIS) andauto-focus (AF) in single and/or dual-aperture (“dual-optical module”)digital cameras.

BACKGROUND

In recent years, mobile devices such as cell-phones (and in particularsmart-phones), tablets and laptops have become ubiquitous. Most of thesedevices include one or two compact cameras: a main rear-facing camera(i.e. a camera on the back side of the device, facing away from the userand often used for casual photography) and a secondary front-facingcamera (i.e. a camera located on the front side of the device and oftenused for video conferencing).

Although relatively compact in nature, the design of most of thesecameras is very similar to the traditional structure of a digital stillcamera, i.e. they comprise an optical component (or a train of severaloptical elements and a main aperture) placed on top of an image sensor.The optical component (also referred to as “optics”) refracts theincoming light rays and bends them to create an image of a scene on thesensor. The dimensions of these cameras are largely determined by thesize of the sensor and by the height of the optics. These are usuallytied together through the focal length (“f”) of the lens and its fieldof view (FOV)—a lens that has to image a certain FOV on a sensor of acertain size has a specific focal length. Keeping the FOV constant, thelarger the sensor dimensions (e.g. in a X-Y plane) the larger the focallength and the optics height.

In addition to the optics and sensor, modern cameras usually furtherinclude mechanical motion (actuation) mechanism for two main purposes:focusing of the image on the sensor and optical image stabilization(OIS). For focusing, in more advanced cameras, the position of the lensmodule (or at least one lens element in the lens module) can be changedby means of an actuator and the focus distance can be changed inaccordance with the captured object or scene. In these cameras it ispossible to capture objects from a very short distance (e.g., 10 cm) toinfinity. The trend in digital still cameras is to increase the zoomingcapabilities (e.g. to 5×, 10× or more) and, in cell-phone (andparticularly smart-phone) cameras, to decrease the pixel size andincrease the pixel count. These trends result in greater sensitivity tohand-shake or in a need for longer exposure time. An OIS mechanism isrequired to answer the needs in these trends.

In OIS-enabled cameras, the lens or camera module can change its lateralposition or tilt angle in a fast manner to cancel the handshake duringthe image capture. Handshakes move the camera module in 6 degrees offreedom, namely linear movements in three degrees of freedom (X, Y andZ), pitch (tilt around the X axis), yaw (tilt around the Y axis) androll (tilt around the Z axis). FIG. 1 shows an exemplary classical fourrod-springs (102 a-d) OIS structure in a single-aperture camera module100. The four rod-springs are rigidly connected to an upper frame 104which accommodates usually an AF actuator (not shown) that moves thelens module 106. This structure allows desired modes of movement in theX-Y plane (translation), FIG. 1a , but also allows a mode of unwantedrotation (torsion) around the Z axis, FIG. 1b . The latter may be due toa combination of several causes such as asymmetric forces applied by thecoils or by a user's (or phone) movements, imperfections of therod-springs and the high rotational compliance of the four-springrod-spring+frame structure.

In the case of a centered single-aperture camera module, the rotationaround the Z axis (according to the exemplary coordinate system shown inFIG. 1) does not affect the image quality severely, since the lens isaxisymmetric. However, this does affect OIS in a dual-camera module,FIG. 2A. FIG. 2A shows in (a) a rotation mode around an axis 202 (in thefigure, parallel to the Z axis) that is roughly centered between twocamera modules 204 and 206 of a dual-aperture camera 200. Because of thelocation of rotation axis 202, the rotation may cause significantdeterioration of the image quality. The rotation causes each lens toshift away in undesired directions (shown by arrows in FIG. 2A(b)) in anunpredictable way. The result is motion blur of the image and a shift ofthe two lenses in opposite Y directions that results in decenter betweenimages received by each camera module and therefore potentially in acatastrophic influence on fusion algorithm results.

Yet another problem may occur in a folded optics zoom dual-aperturecamera, such as a camera 250 shown in FIG. 2B. Such a camera isdescribed for example in detail in co-owned international patentapplication PCT/IB2016/052179. Camera 250 includes a “folded” cameramodule 252 with a first optical axis 270 and an upright (non-folded)camera module 254 with a second optical axis 272 perpendicular to axis270. A 90° folding of an optical path parallel to axis 272 to an opticalpath parallel axis 270 is performed by an optical path folding element(OPFE) 274. The OPFE may exemplarily be a prism or mirror. Among othercomponents, folded camera module 252 comprises a lens actuationsub-assembly for moving a lens module 256 (and a lens therein, which isreferred to henceforth as “folded lens”) in the X-Y plane. The lensactuation sub-assembly includes a hanging structure with four flexiblehanging members (i.e. the “rod-springs” referred to above) 258 a-d thathang lens module 256 over a base 260. In some exemplary embodiments,hanging members 256 a-d may be in the form of four wires and may bereferred to as “wire springs” or “poles”. The hanging structure allowsin-plane motion as known in the art and described exemplarily inco-owned U.S. patent application Ser. No. 14/373,490. Exemplarily, afirst movement direction 262 of the lens is used to achieve AF and asecond movement direction 264 is used to achieve OIS. A third movement,an unwanted rotation 266 of the lens about an axis parallel to the Zaxis as described above actually causes an unwanted effect of dynamictilt of the lens (the lens' optical axis may not be perpendicular to thesensor's surface due to that rotation) and may result in images that areusually sharp on one side and blurry on the other side. The actuators insuch cameras are typically voice coil magnet (VCM) actuators. A majorproblem with known VCMs that provide (X, Y)-direction OIS movement andZ-direction AF movement is that the VCMs are larger along the X and Yaxes than the moved lens module.

It would be advantageous to have a folded camera module with both AF andOIS mechanisms, where the incorporation of such mechanisms andcapabilities should follow standard manufacturing processes and shouldnot result in penalty in camera height. It would be further advantageousto have a folded-lens dual-aperture camera that incorporates such afolded camera module.

SUMMARY

In various exemplary embodiments there are provided folded cameramodules having respective folded camera module heights, each foldedcamera module comprising a lens module carrying a lens having a firstoptical axis, an image sensor positioned at a first end of the foldedcamera module, a first actuator positioned at a side of the cameramodule and operable to provide a first movement of the lens module in afirst (“focusing”) direction parallel to the first optical axis, asecond actuator positioned at a second end of the camera module andoperable to provide a second movement of the lens module in a second(“height”) direction perpendicular to the first direction, wherein thefolded camera module height is defined by a diameter of the lens moduleand by a range of the second movement, and a third actuator positionedat the second end of the camera module and operable to provide a thirdmovement of the lens module in a third (“width”) direction perpendicularto both the first and second directions.

In an exemplary embodiment, an actuator dimension for each actuator inthe direction of the camera height is smaller than the camera height.

In an exemplary embodiment, the folded camera module further comprisesan OPFE configured to fold an optical path parallel to the firstdirection toward the first direction.

In an exemplary embodiment, the first movement is enabled by a pluralityof rolling balls engaged in a plurality of grooves formed in a memberattached to the lens module.

In an exemplary embodiment, the first movement is enabled by a pluralityof leaf springs attached to the lens module.

In an exemplary embodiment, the second and third movements are enabledby leaf springs attached to a static part of the folded camera modulelocated between the OPFE and the image sensor.

In an exemplary embodiment, the plurality of rolling balls and theplurality of grooves are dimensioned so as not to increase the foldedcamera module height.

In an exemplary embodiment, the plurality of leaf springs is dimensionedso as not to increase the folded camera module height.

In an exemplary embodiment, the folded camera module further comprises afourth actuator positioned at the second end of the camera module andoperable to provide a fourth movement to avoid roll around the firstoptical axis, the fourth actuator having an actuator dimension in thedirection of the camera height smaller than the camera height.

In some exemplary embodiments, the OPFE, is a prism. In some suchembodiments, the lens module is rigidly attached to the prism, forming alens-prism unit.

In some exemplary embodiments, the folded camera module is included witha second camera module in a dual-aperture camera. The second cameramodule may be an upright camera module with a second optical axisparallel to the second direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting examples of embodiments disclosed herein are describedbelow with reference to figures attached hereto that are listedfollowing this paragraph. The drawings and descriptions are meant toilluminate and clarify embodiments disclosed herein, and should not beconsidered limiting in any way. Like elements in different drawings maybe indicated like numerals.

FIG. 1 shows a camera module with an exemplary classical fourwire-springs OIS structure: (a) modes of wanted X-Y translations, and(b) mode of unwanted rotation around the Z axis;

FIG. 2A shows a dual-aperture camera in (a) rotation mode around an axisroughly centered between two camera modules, and (b) movement of eachlens in undesired directions;

FIG. 2B shows a dual-camera module with a folded optics camera module;

FIG. 3A shows schematically an isomeric view of a first exemplaryembodiment of a folded camera module disclosed herein;

FIG. 3B shows schematically a first exploded isomeric view of the foldedcamera module of FIG. 3A;

FIG. 3C shows schematically a second exploded isomeric view of thefolded camera module of FIG. 3A;

FIG. 4A shows schematically an isomeric view of a second exemplaryembodiment of a folded camera module disclosed herein;

FIG. 4B shows schematically two exploded isomeric views of the foldedcamera module of FIG. 4A;

FIG. 4C shows schematically the small change in total camera height dueto lens module X-axis movement;

FIG. 5A shows schematically an isomeric view of a third exemplaryembodiment of a folded camera module disclosed herein;

FIG. 5B shows schematically an exploded isomeric view of the foldedcamera module of FIG. 5A.

DETAILED DESCRIPTION

In the description below the following system of X-Y-Z coordinates ischosen exemplarily and for explanation purposes only: the Z axis isparallel to the optical axis of the lens module of the folded cameramodule described below (referred to as “first” optical axis), whereasthe X and Y axes are perpendicular to the Z axis and to each other andform a plane parallel to that of the folded camera image sensor, seee.g. FIG. 3. The X axis is also parallel to a “second” optical axis likeaxis 272 in FIG. 2B.

FIG. 3A shows schematically an isomeric view of a first embodiment of afolded camera module numbered 300 according to an example disclosedherein. FIG. 3B shows schematically a first exploded isomeric view offolded camera module 300 and FIG. 3C shows schematically a secondexploded isomeric view of the folded camera module 300. Like cameramodule 100 above, camera module 100 can exemplarily be included(incorporated) in a folded-lens dual-aperture camera like camera 250 orother cameras described in co-owned US patent application No.20160044247. Camera module 300 comprises an image sensor 302 positionedat a first end 303 of camera module 300 and having an imaging surface inthe X-Y plane, a lens module 304 with a first optical axis 306 parallelto the Z axis, and an OPFE in the form of a prism 308 having areflecting plane 310 with a normal tilted at 45 degrees to the imagesensor surface, such that light arriving from the X direction is tiltedby the prism to the Z direction. The OPFE, will henceforth be referredto generically as “prism”, with the understanding that it can also be amirror or any other reflecting element Lens module 304 is rigidlycoupled to the prism and the two elements form a single “lens-prismunit” 324 (such that the lens and prism move together). In contrast withcamera module 100, camera module 300 comprises a combined lens and prismactuation assembly (also referred to as lens-prism actuation assembly)for moving lens-prism unit 324 in three directions X-Y-Z. The lens-prismactuation assembly includes a hanging structure 316 comprising fourflexible hanging members 316 a-d that hang the lens-barrel unit betweenvertical sections 312 a or 312 b rigidly coupled to a base 318 and to amoving support structure 330. Members 316 a-d may be in the form of fourwires and may be referred to as “wire springs” or “poles”. Hangingstructure 316 allows X-Y motion as known in the art. Support structure330 is shown exemplarily as having a U-shape, with two side members 320a and 320 b and a back frame 322. The back panel is positioned at asecond end 321 of the folded camera module, which is opposite to thefirst end along the first optical axis. Hanging members 316 a-d extendbetween vertical sections 312 a and 312 b and side members 320 a and 320b.

Note that as used herein, the terms “first end” and “second end” are notnecessarily limited to physical ends of the folded camera module, butrather relate to positions along an optical path: the first end is inthe optical path before the prism and/or the folded lens module, as inFIGS. 3A-C herein, while the second end is in the optical path after thefolded lens module and/or an additional prism (the latter for example asin a folded camera module shown in FIG. 3 of co-owned US patentapplication No. 20160044247).

In camera module 300, the lens-prism actuation assembly comprises fouractuators (e.g. voice coil motors or “VCM”s), each actuator including arespective magnet and coil. Thus, a first actuator comprises a magnet326 a and a coil 328 a, a second actuator comprises a magnet 326 b and acoil 328 b, a third actuator comprises a magnet 326 c and a coil 328 cand a fourth actuator comprises a magnet 326 d and a coil 328 d. Thefirst, second and third actuators are operable to impart to thelens-prism unit an in-plane motion relative to base 318 in substantiallythe X-Y plane, e.g. for OIS. These actuators are also operable to avoidlens-prism unit rotation (tilt) motion around the Z-axis. The fourthactuator is a “side” actuator, operable to impart the lens-prism unit amotion along the Z-axis for focusing (i.e. for autofocus). As shown inthe exploded view in FIG. 3B, magnets 326 a, 326 b and 326 c arepositioned on back panel 332 that is parallel to back frame 322, whilemagnet 326 d is positioned on a side panel 340 that is rigidly attachedto the lens. Coils 328 a, 328 b and 328 c are positioned on a back board332 facing respective magnets 326 a, 326 b and 326 c on back panel 332,while coil 328 d is positioned on a side board 334 that is rigidlyattached to side member 320 b. The first, second and third actuators arealso referred to as “back actuators” while the fourth actuator is alsoreferred to as “side actuator”. Position sensors (for example Hall barposition sensors) 336 are provided for each magnet-coil pair. Forexample, a Hall bar sensor 336 a is positioned in proximity to magnet326 a, a Hall bar sensor 336 b is positioned in proximity to magnet 326b, a Hall bar sensor 336 c is positioned in proximity to magnet 326 cand a Hall bar sensor 336 d is positioned in proximity to magnet 326 d.The movement along the Z axis for focusing, actuated by the sideactuator, is enabled by two sets of rolling balls 350 a and 350 barranged to engage and be positioned between two grooves 352 a and 352 bin side board 334 and two grooves 354 a and 354 b in side panel 340, asknown in the art.

Advantageously, all four actuators are positioned so as not to addheight to the folded camera module. The folded camera module height issolely determined by the diameter of the lens module and its movementrange in the X direction (see also FIG. 4). The positioning of the sideactuator components—magnet 326 d on side panel 340 and of coil 328 d onside board 334—is also advantageous for providing the Z directionmovement without impacting camera module height. Further advantageously,the positioning of the actuators is such that they do not block orinterfere with an optical path between on object being imaged and thefolded camera module image sensor. Specifically, the prism is positionedbetween the actuators used for OIS and the image sensor. Furtheradvantageously yet, a camera module disclosed herein may be low costmanufactured with proven technology.

In operation, a Lorentz force may be applied on magnets 326 a-b alongthe X axis direction and on magnet 326 c along the Y axis direction.Having these three forces on the three magnets allows three mechanicaldegrees of freedom in the motion of the center of mass of the lens andprism: linear X and Y motions and tilt around Z axis motion. The X-Ymotion of the lens-prism unit can be measured by the respective Hallbars coupled to the magnetic field created by the respective magnets.Similarly, a Lorenz force may be applied by magnet 326 d along the Zdirection to allow linear motion along the Z axis. More details aboutthe operation of the various actuators may be found in co-owned patentapplication No. PCT/IB2016/052179.

FIG. 4A shows schematically an isomeric view of a second embodiment of afolded camera module numbered 400 according to an example disclosedherein. FIG. 4B shows schematically two exploded isomeric views offolded camera module 400, while FIG. 4C shows schematically the smallchange in total camera height due to lens module X-axis movement incamera module 400 as well as the total height dimension H. In general,embodiment 400 includes the same components as embodiment 300, exceptthat the lens module is decoupled from the prism. The lens is movable inthe X-Y plane while the prism is fixed (not moving). Since the lens isaxisymmetric and the prism is fixed, tilt around Z does not affect thequality of an image obtained at the image sensor. For this reason,camera module 400 may include only three of the four actuators, i.e.only actuators 324 b-d, since actuator 324 a is not needed for the X-Yin-plane movement. Consequently, only three Hall-bar sensors are neededfor position sensing. Of these, only 326 b and 326 c are shown. Thechange due to the lens module movement (i.e. the lens module movementrange) is equal to the distance between by two extreme lens modulepositions, a lower position marked by 402 and an upper position markedby 404. The total height H of the folded camera module is determined bythe lens module diameter D plus the change due to the lens modulemovement.

FIG. 5A shows schematically an isomeric view of a third embodiment of afolded camera module numbered 500 according to an example disclosedherein. FIG. 5B shows schematically an exploded isomeric view of thefolded camera module 500. In contrast with camera modules 300 and 400,in camera module 500 the movement along the Z axis for focusing isenabled by a hanging structure comprising four flexible hanging members502 a-d that hang the lens-barrel to side board 334. This removes theneed for rolling balls and grooves. Members 502 a-c may be leaf springs.Members 502 a-d are mechanically coupled to lens module 304 through apanel 504 that is rigidly attached to the lens module. Actuation by theside actuator (of which only the magnet 326 d is shown) causes flexingof members 502 a-d in the Z-direction, allowing the Z-movement of thelens module for AF.

All patents and patent applications mentioned in this application arehereby incorporated by reference in their entirety for all purposes setforth herein. It is emphasized that citation or identification of anyreference in this application shall not be construed as an admissionthat such a reference is available or admitted as prior art.

While this disclosure has been described in terms of certain embodimentsand generally associated methods, alterations and permutations of theembodiments and methods will be apparent to those skilled in the art.For example, while the incorporation of a folded camera module describedherein in a dual-aperture camera is described in some detail, a foldedcamera module may be incorporated in a multi-aperture camera with morethan two camera modules. For example, while the use of Hall bars asexemplary position sensors is described in detail, other positionsensors (for example MEMS-type) may be used for purposes set forthherein. The disclosure is to be understood as not limited by thespecific embodiments described herein, but only by the scope of theappended claims.

What is claimed is:
 1. A folded camera module having a respective foldedcamera module height and first and second ends, comprising: a) anoptical path folding element (OPFE) configured to fold an optical pathfrom a second direction to a first direction, the first direction beingperpendicular to the second direction; b) an image sensor positioned atthe first end and perpendicular to the first direction; c) a lens modulecarrying a lens having a fixed focal length and a first optical axisparallel with the first direction, the lens positioned between the OPFEand the image sensor; d) a first voice coil motor (VCM) operable toprovide a first movement of the lens module in the first direction; e) asecond VCM having a second VCM movement range and positioned at thesecond end and operable to provide a second movement of the lens modulein the second direction; f) a third VCM positioned at the second end andoperable to provide a third movement of the lens module in a thirddirection perpendicular to both the first and second directions, whereinthe first VCM is positioned at a side of the camera module toward thethird direction, and wherein the folded camera module height is definedby a diameter of the lens module and by the second VCM movement range,wherein the motion in the first direction is for focus, and wherein themotion in the second and third directions is for optical imagestabilization.
 2. The folded camera module of claim 1, wherein the firstmovement is enabled by a plurality of rolling balls engaged in aplurality of grooves formed in a member attached to the lens module. 3.The folded camera module of claim 2, wherein the plurality of rollingballs and the plurality of grooves are dimensioned so as not to increasethe folded camera module height.
 4. The folded camera module of claim 1,wherein the first movement is enabled by a plurality of springs attachedto the lens module.
 5. The folded camera module of claim 4, wherein theplurality of springs is dimensioned so as not to increase the foldedcamera module height.
 6. The folded camera module of claim 1, whereinthe second and third movements are enabled by springs attached to astatic part of the folded camera module.
 7. The folded camera module ofclaim 1, wherein the OPFE is a prism.
 8. The folded camera module ofclaim 1, wherein the OPFE is a mirror.
 9. The folded camera module ofclaim 1, wherein the OPFE is fixed relative to the first, second andthird VCMs.
 10. The folded camera module of claim 1, wherein the lensmodule is rigidly attached to the OPFE.
 11. The folded camera module ofclaim 1, further comprising a fourth VCM positioned at the second endand operable to provide a fourth movement to avoid roll around the firstoptical axis, the fourth VCM having an VCM dimension in the direction ofthe camera height smaller than the camera height.
 12. The folded cameramodule of claim 11, wherein the first movement is enabled by a pluralityof rolling balls engaged in a plurality of grooves formed in a memberattached to the lens module.
 13. The folded camera module of claim 12,wherein the plurality of rolling balls and the plurality of grooves aredimensioned so as not to increase the folded camera module height. 14.The folded camera module of claim 11, wherein the first movement isenabled by a plurality of springs attached to the lens module.
 15. Thefolded camera module of claim 14, wherein the plurality of springs isdimensioned so as not to increase the folded camera module height. 16.The folded camera module of claim 11, included with a second cameramodule in a dual-aperture camera.
 17. The folded camera module of claim16, wherein the second camera module is an upright camera module with asecond optical axis parallel to the second direction.
 18. The foldedcamera module of claim 1, included with a second camera module in adual-aperture camera.
 19. The folded camera module of claim 18, whereinthe second camera module is an upright camera module with a secondoptical axis parallel to the second direction.